1. Field of the Invention
The present invention relates to a turbo compressor, and in particular to an improved turbo compressor which is capable of minimizing the size of a compressor, enhancing a compression efficiency, and minimizing the leakage of a refrigerant gas by providing an improved refrigerant gas flow path capable of decreasing a pressure difference between a compression chamber and a motor chamber.
2. Description of the Conventional Art
Generally, the compressor is an apparatus for compressing a gas such as air, a refrigerant gas etc. by a rotation operation of an impeller or a rotor and a reciprocating operation of a piston.
The above-described compressor is formed of a driving force generation unit for driving an impeller, a rotor, and a piston and a compression mechanism for sucking and compressing gas by a driving force transferred from the driving force generation unit.
The above-described compressor is classified into a hermetically sealed type compressor and a separation type compressor in accordance with an installed position of the driving force generation unit and the compression mechanism. The hermetically sealed type compressor is formed of a hermetically sealed container in which the driving force generation unit and the compression mechanism unit are installed. In the separation type compressor, the driving force generation unit is installed outside the hermetically sealed container for thereby transferring the driving force generated by the driving force generation unit to the compressor mechanism unit installed in the hermetically sealed container.
In addition, the conventional hermetically sealed compressor is classified into a rotation type compressor (so-called, a rotary compressor), a reciprocating type compressor, a scroll type compressor, etc. in accordance with the structure for compressing gas. A container type mechanism is formed in each of the above-described compressors for compressing gas by decreasing the volume of the same.
Among the above-described container type compressors, in the rotation type compressor, an eccentric shaft is installed in a cylinder having a cylindrical space therein and is rotated for thereby decreasing the volume of the space therein, so that the gas in the space is compressed. In the reciprocating type compressor, a piston reciprocates within the cylinder for thereby decreasing the volume of the inner space of the cylinder, so that the gas in the space is compressed. In the scroll compressor, upper and lower scrolls each having an involute curve type wrap are engaged with each other and are rotated for thereby pressurizing the gas therein by decreasing the volume of the inner space of the compressor.
However, the conventional rotational type compressor and reciprocating type compressor are not expensive but generate much vibration noise when pressurizing the gas, and the compression efficiency is low.
In addition, the scroll compressor has small vibration noise and high compression efficiency when continuously pressurizing the gas, the number of parts is large for thereby increasing the fabrication cost.
Furthermore, the conventional scroll compressor uses a high pressure refrigerant gas, the size of the same is bulky, and the same is heavy. When adapting this kind of the compressor to a home appliance, the size of the home appliance is increased, and the same is heavy, so that it is very difficult to handle the same.
In order to overcome the above-described problems, a turbo compressor is introduced, which is basically directed to generating a pressure difference using a centrifugal force. In the turbo compressor, an impeller is rotated using a driving force of a motor, and a gas such as air and refrigerant gas is sucked and then compressed using the centrifugal force generated when the impeller is rotated.
FIG. 1 is a cross-sectional view illustrating the construction of a two-stage compression type turbo compressor filed in Korea Industrial Property Office and having Ser. No. 97-64567. As shown therein, in the conventional turbo compressor, a first compression chamber 111 communicating with an accumulator A and a second compression chamber 112 communicating with a condenser (not shown) are installed at both sides in the interior of a hermetically sealed container 110.
A motor chamber 113 in which a brushless DC motor 120 is installed is formed at the inner center portion of the sealed container 110.
The interiors of the first and second compression chambers 111 and 112 and the motor chamber 113 communicate with a gas flow path 114 formed on an outer circumferential surface of the motor chamber 113.
In addition, both ends of a driving shaft 130 engaged with the motor 120 are positioned in the first and second compression chambers 111 and 112, and first and second impellers 140 and 150 are engaged to both ends of the driving shaft 130 for compressing the gas sucked by the rotation of the same.
A radial bearing 160 is disposed at both sides of the motor 120 for radially supporting the driving shaft 130, and a thrust bearing 170 is disposed to an outer circumferential surface of the driving shaft 130 for axially supporting the driving shaft 130 at both sides of the radial bearing 160.
In the first and second compression chambers, there are provided first and second impellers 140 and 150 for increasing the kinetic energy by accelerating the suction refrigerant gas, and first and second diffusers 111a and 112a and first and second volute portions 111b and 112b are formed therein for converting the kinetic energy into a constant pressure.
At this time, the first and second impellers 140 and 150 installed in the conventional turbo compressor are formed to have an outer diameter smaller than the inner diameter through which the gas is discharged. Namely, the first and second impellers 140 and 150 are formed in a conical shape (back to back shape).
In addition, an inlet through hole 113a for guiding a part of gas from the gas flow path 113 into the interior of the motor chamber 113 through the first compression chamber 111 for cooling the motor and an outlet through hole 113b for guiding the flow of gas flown into the motor chamber 113 through the inlet through hole 113a and cooled the motor chamber 113 to the second compression chamber 112 through the gas flow path 114.
In the drawings, reference numeral 110a represents a refrigerant gas suction port, and 110b represents a refrigerant gas discharge port.
The operation of the conventional turbo compressor will be explained.
When an electric power is supplied to the motor 120, a magnetic force is induced. The driving shaft 130 is rotated at a high speed by the thusly generated force, so that the first and second impellers 140 and 150 fixed to both ends of the driving shaft 130 are rotated.
Continuously, the refrigerant gas is sucked into the compression chambers 111 and 112 by the rotation of the impellers 140 and 150 and is sprayed in a screw shape by the centrifugal force of the impellers 140 and 150 and is introduced into the volute portions 111b and 112b through the diffusers 111a and 112a. During this process, the refrigerant gas is compressed by an increase of the pressure head and then is discharged to the condenser (not shown) through the discharge port 110b.
The refrigerant gas is sucked from the accumulator A into the first compression chamber 111 by the rotation of the first impeller 140 and is accelerated by the first impeller 140.
The thusly accelerated refrigerant gas passes through the first diffuser 111a and is flown into the first volute portion 111b for thereby implementing a first compression, and the thusly first compressed gas is sucked into the second compression chamber 112 through the gas flow path 114.
Continuously, the first compressed gas sucked into the second compression chamber 112 is accelerated by the second impeller 150, and the thusly accelerated first compressed gas passes through the second diffuser and is flown into the second volute portion 112b for thereby implementing a second compression thereby and then is discharged to the discharge port 110b.
At this time, a seal (Labyrinth seal) 141 is formed at the inner portions of the first impeller 140 and the second impeller 150 for thereby preventing the refrigerant gas from being leaked into the motor chamber.
In the conventional turbo compressor, a part of the first compressed refrigerant gas flowing through the gas flow path 114 flows into the interior of the motor chamber 113 through the inlet through hole 113a formed on the wall surface of the motor chamber 113, and the thusly introduced gas cools the elements in the motor chamber 113, in which the motor 120 is installed, and flows to the gas flow path 114 through the outlet through hole 113b and is sucked into the second compression chamber 112. Since the driving shaft 130 rotates in a load-free state, the driving shaft 130 may be radially and axially moved. However, the above-described radial and axial movements are prevented by the bearing 170.
In the thusly constituted turbo compressor, since the inlet and outlet through holes communicating with the gas flow path are formed between the first and second compression chambers, and then the first compressed high temperature compression gas cools the motor, the cooling efficiency of the motor may be decreased.
In addition, since the accumulator is additionally installed for fully generating a refrigerant gas introduced into the first compression chamber, the construction of the system is complicated.
Since the first and second impellers are installed in a conical shape (back to back shape), when the compressed refrigerant gas is discharged, a seal is needed for preventing the compressed refrigerant gas from being leaked from the motor chamber.